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Sept. 2, 1947. W, -QHAFEE MULTISTATION HEI GHT FINDER 5 Sheets-Sheet l INVENTOR,

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Filed June '7, 1941 3947- E. w. CHAFEE 2,426,596

MULTISTATION HEIGHT FINDER Filed June 7, 1941 5 Sheets-Sheet 2 JNVENTOR, 2542A W CHA FEE, BY

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MULTISTATION HEIGHT FINDER Filed June 7. 1941 5 Sheets-Sheet 4 INVENTOR; 5424 M fi/AFEE,

ATTOE x ept 2, E. w. CHAFEE MULTISTATION HEIGHT FINDER 5 Sheets-Sheet 5 Filed June 7, 1941 E F m% M m m, WW mV 1. WE]

Patented Sept. 2, i947 UNIT ED llIULTISFDATION HEIGHT FENDER,

Ear-l Ohafee, New York, N. 3. as'signor-to Sperry Gyroscope Company, 11-110., .Brooklyn, 'N.-:Y.,1a corporation of NewzYork Application June 17., 1941,;SeriaTNo. 396,988

"20- Claims. '1

"This invention relates-to improvements in altimeters -or height finders of the multi-station or 'long base "type. According't'o my invention, I make use of the altimetric roofprinci-p1e in the determination of "altitude, which per se "is known intheart.

"One objectof theinvention 'isto produce a continuous solution for altitude in 13311 instrument of this type so that as the target is followed at either or *both stations; the altitude iscontinuous'ly given in a form suitable "for feeding into an antiaircraftpredictor continuously.

Another object of "the invention is toso design the apparatus that the two stations maybe at-a different altitude without affectingthe accuracy of the device or the continuous fiow' of data.

Another object o'f'the invention is to sodesign the devicezthat it may be used with stations of different tlistances between-them or in different directions, and also so that the device -may be used on bo'th sides of the zenithor, inotherwords, where :the-sig hting' angles are either acute or obtuse.

:A li urther =bbjeet of the invention is to provide a :means -for=show ing =when the device is inoperative and :also for showing the proper -dials to read when the sighting angles are obtuse and acute.

.ReEerring to the drawings showing one form my inventionmaysassume,

:Eig. 1. is.a :diagram -in perspective, showing the pitincipalxportions :of :the computing mechanism atstation P.

'Fig. 22 .is a'esimilar adiagram 'of the-'sightand connecteddzransmitter atsta'tion s.

.wFig. 5313 a .diagraonsshowin the trigonometric principles involved.

Fig.4 tis=ra :Eurth'er-idiagram showing the effect of differences maltitudeof :the :two sighting stations.

F!ig.--.5 is .a'wifingudiagram :of the electrical transmission .system .1 employed between v the two stations.

Fig. -6 is :a plan (diagram, in simplified formmf the mechanism shownsinFig. :1.

7 is a front elevation of the computing deviceat-si hting'station P.

'Eig. 8 .is aiaceviiew .011 a larger scale of'the base:line;pointer:dial.

-=Fig. :9 :is :a verticalsection of the same en' line 9-.9of EigxS.

Fig-:10 .is a::face' :view zo'f a. modified iform "of dial shown. iniFiigstz'fl and 9,"the-variable speed drives being shown. .-.in :diagrammatic form.

*Ei l'lsisya. diagrammatic J-view of a modified formoftheinvention.

:Rierllillg first to Fig-3, it is assume'd' that =station .P :and s'tationzs :are :at1;a,=distance apart' b. PwBA is. ahorizontal. lanecontainin 1), and PT'n-isaa vertical planealsoscontaining b. TT' BA is a verticalplane perpendicular to theme other planes and containing the target '1. I'he sighting angl'es 1 and-n2 determine the slant planes PaTT and *Sb'T-I" which intersect on the horizontal "line -'TT', which lineis knownas the peak of thealtimetric roo'f. All points in the line TT' have the same altitude, -i."e., Til=TB=Ho-"(the unknown-altitude). A consideration dfthisfigur 'wi-l'l show that the -unknown-a1titude Hois the common altitudeof the two triangles PAT and SA'I" -of-"which the angles 1 and-qaz are both known. The dis-tance between'the "two stations -P and S 5) is also-known. By my inVention -I provide =a mechanical means for continuously solving for the unknown --altitude --of a -moving target by simpletrigonometricalfunctions. Thus, the=fol1owing equati0nsmay loo-written:

onthesedundtions may be set 'upas'tangent' functions asshown hereinafter.

The a'boveequations hold g'ood whether'thettarget is "-to the right-of the stations? and -S,"Where thG EmQIBS'q VaHd11523138"3011EQ, or-toithe ieitof the stations--1 and- S; where such angles are both obtuse,- provided "distances measured to; the "right are considered, say,;"positive andflistancesmeasured to 'the' left are considered :of opposite sign. In case, howeventhe target is almost :directly overheadythat is; lies between the points? .andS, the solution proposed by the present invention becomes indeterminate. -In such "case, 'iit may readily be seen-"that one oftheangl'es 51 7011 2 is acute and the other obtuse. In-"a'llcasesfhoweuer, 2 1.

Even if th'e *two' stations and "S are .IIOt. at the same -a'-ltitu'de, the-same generalrsdlution .applies, as-indicatedinFig. 4. In this figure, the iiifierence in altitude ofthe stations P andS is shown as AH and therefore, in thiscase the above Equation 1 becomes At sighting-station P'is shown 'thesight'. I IFigs. 1 and 7) --rotatab1ymounted in elevation (e1) and in the s'lantp'lane determined "by 1. "Said sight may lie-provided with double. eye -pieces 2 and 3, eitherone of Which-may beusedgdepending upon Whi'ch one is in the best positionto.lo'okthrough as the'sight is revolvedin elevation. Freedom -in elevation is provided by mounting the sightffor rotation about the-horizontal axis of sha'ft "4 ..to g ivethe angle -1,-andit m'ay'rbeturned about an axispperpendicularthereto, in .other WOrd5,-. about theaxis of the eye'jpieces to .give the angle ,Qi. Rotationabout the latter "axis maybe done directly by moving the sights by hand, the angle ,81 being shown on scale 5. Movement in elevation through the angle 1, however, is shown as obtained by rotating the handwheel 6 which turns, through a pinion 1 and gear 8, a second shaft 9 on which is mounted the sight angle scale l and a long pinion H. Gear 8 is shown as driving a larger gear l2 on shaft 4 so that rotation of the gear 12 rotates the sights in elevation. The rotation of the long pinion II turns, through meshing gear l3, a three-dimensional cam l4 laidlout circumferentially in a cotangent function of the angle 1 and longitudinally in a function of He.

Said cam is positioned longitudinally from the Ho handwheel l5 on a threaded shaft l6 threaded in an adjustable carriage l'l within which is mounted the fixed shaft E8 on which cam I4 is journaled. Therefore, by rotating handwheel I5, the cam is moved longitudinally and each successive transverse section is increased with IE0. Cam [4' for station S is similarly desi ned.

On cam M is a lift pin I!) having rack teeth thereon which mesh with the pinion 2| on shaft 22. The lift of said pin therefore is proportional to Ho cot 1 or, in other words, to L1. Rotation of said shaft 22 turns, through a second pinion 23 and gear 24, an annular scale and reference index 25 which may be graduated in feet or other unit of distance, and the position of which with reference to a stationary index 26 represents the unknown distance L1 of Fig. 3.

Similarly, the cam M for station S is rotated through the angle 2. This may be conveniently effected by some form of electrical transmission system such as a potentometer 28 on the horizontal shaft 4' of the sight I at station S, said sight being rotated from the'handwheel 6', Potentiometer 28 (Fig. 5) is shown as a circular resistance having three equipositioned taps connected similarly to a second potentiometer 28 of similar form at the primary station. Each potentiometer has rotatable sliding brushes 29, 3D and 29', 33', the former brushes being shown as mounted on the shaft 4'. The potentiometer 28, on the other hand, is shown as mounted on a shaft 3| rotated through suitable gearing from the long pinion 32 on the shaft 33 of the handwheel 34. The operator of the handwheel 34 rotates the same until the potentiometer 28' is in the same relative position as potentiometer 28 or, in other words, until the milliammeter 35 con nected to the latter reads zero (Figs. 1 and 5). 7

By this means I have provided a simple transmission system between the two station P and S, but it is obvious that other types of transmission systems could be substituted, using either full power control or manual supplemental power, as

desired.

The scale 38 on shaft 33 therefore shows the angle 4:2 and position the cam I4, which is geared to the pinion 32, through the angle 2. Cam Id, like cam I4, is journale'd in the carriage I! so that it is likewise adjusted from the Ho handwheel I5. The lift of the pin I9 thereon therefore represents L2 of the diagram and is shown as positioning the two pointers 31 and 38 readable with reference to the index 25, and both of which are connected to rotate with the shaft 39 of the pinion 40 meshing with the rack teeth 4| on the pin l3. From the equations and from the diagram of Fig. 3 it will be seen that L1=L2+b. Therefore the pointers 3'! and 38 are initially set apart by knob 42 through a distance on the scale 43 equal to 2b. In other words, one pointer is set through the distance I) in one direction from 4% the mutual zero and the other pointer through the distance I) from zero in the other direction to take care of the reversal in sign as the sights pass through the zenith,

For this purpose, the pointer 3'5 is shown as secured to the face of a gear it secured to a sleeve rotatably mounted on shaft 42' of knob 42. Pointer 38 is similarly secured to the face of a similarly mounted gear ll. On the inner end of knob 42 is shown a pinion l2 meshing with a gear 73 on the shaft of the elongated pinion (it which meshes both with the gear H and a second elongated pinion 6!, the latter meshing with the aforesaid gear Hi. When knob 42 is rotated, therefore, the pointers 3! and 38 are either spread apart or brought together, at all times maintaining the distance 1) between the zero index and each pointer, as shown on scale 43. It will also be seen that since the entire gear train connected with the pointers is supported by the framework M which is secured to and rotates with the shaft 39, the two pointers will be moved together through the same angle as turned by the shaft 33.

The operator of the handwheel l5 then rotates the same until the index 25 coincides with the selected pointer 3'! or 33, these pointers being of distinctive colors, say red and White, one of the pointers being used when both angles 51 and 422 are acute and the other when both angles are obtuse. in order to show automatically which pointer to use, I have shown in Fig. 6 a cam 44 connected to rotate with the sight I and adapted to close spring contacts 35 when the sighting angle of the sight I is acute and thereby light the white signal lamp 46, which shOWs that the white pointer 31 should be matched with the index 25. Similarly, I provide a cam 44' to be rotated from the sight S or the equivalent handwheel 34, which is designed so as to be opened when the sighting angle is acute and closed when it is obtuse. Therefore the white light 46 is lighted and the red light 46' extinguished when the angles are acute, and the red light 46' lighted and the white light 46 extinguished when the angles are obtuse. On the other hand, when one angle is acute and the other is obtuse, bot-h lights are either off or on, in which case the observer continues to crank in the original direction of movement until one of the lamps lights up.

A consideration of Equation 1 will show that when the operator turns the crank E5 to match index 25 with one of the selected pointers 31 or 33, the operator is really inserting the unknown H0 into this equation, so that the angular distance that the handle is rotated is a measure of the altitude H0. This may therefore be read on the indicator 2? geared thereto. a

In order to provide for diiference in elevatio between the stations, i. e., AH, I have shown in Figs. 1 and 6 a fourth handwheel 53 provided with a graduated dial 5! and having an interiorly threaded hub 52 in which is threaded a sleeve 53 rotatably but non-slidably mounted on the shaft 54 of the cam I4. Therefore, by adjusting the handwheel, the cam hi may be adjusted longitudinally independently of the cam [4, although it is moved bodily with the carriage I! and cam :4 when handwheel I5 is adjusted. By this means, the difference in altitude (AI-I) between the stations may be inserted on the cam I4, and it will readily be seen, therefore, that in this case Equation 2 is solved by the turning of crank 15 to match the index 25 and the selected pointer 37 or 38. The altitude thus determineclmay be'read on 5. indicator 27 and is continuously set in the com;- puter or predictor by hand or automatically, as desired.

From the foregoing, some of the advantages of my invention will be apparent. Thus, with my system of continuous flow of data and movement of the follow-the-pointer dials (Figs. 8 and .9), the operator may so operate the handwheels as to average out unevenness in the angular positions of 1 and 1P2 as they come in.

This idea is further developed in Fig. 10, showing a modified form of the indicating mechanism-shown .in Fig. 8. According to this system, there is interposed between the outer rotating dial 25'and the inner-pointers 31 and 38 an intermediate index 80. This index is independently rotatable and is shown as being driven from a Worm 8! on the shaft of the cylinder 32 of a variable speed drive comprising a constant speed motor 83, a disc 85 driven therefrom, and a radially adjustable ball carriage 85 which maybe set from handwheel 86 so that the cylinder 82 is'driven at anydesired'speed ineither direction. In operating the same, the handwheel 85 is adjusted until the index 80 'follows either or both of the follow-the-pointers 25 and 31 or 38, so that a rate change of range is thereby set up. The mechanism will therefore continue to operate even if the target is obscured from one of the sighting stations, since in that case the index 83 will continue to follow the pointer of the sighting station which remains on the target. Thereby the "apparatus will continue to function during a considerable period even though one stationmay be obscured" or put out of action.

It :of course, obvious that theseveral variables involved may .be introduced .in a different manner than described .in the modification shown-in Figs. 1 and fi. ThusinFig. 11, I have shown one of the many variations of which my inyentionis capable. In this. figure, .two threedimensionalacamps are again employed, the .rotationrof one beinggoverned by n andithe rotation of the other by 462. In this case, however, the cams are axially displaced in accordance with L1 and L1 'b, respectively, the cams being laid out in .a tangent function of bi and 2, so that the lift of the two pins are each :proportional'to Ho. Therefore, the cams in this :case simultaneouslyeolve the equations (each involving two unknowns) In this figure, the sight at station P is again shown at .l .and the rotation-of the sight rotates the threeedimensional cam 95! through bevel gears 35!, long pinion H and gear 13. In this case, the carriage or bracket 92 rotatably supporting .thecam is displaced longitudinally .from athreadedshaitfi whichis rotated by a variable speed .drive interposed between the handwheel 94 and the worm 93 so that a rate of change of horizontal-rangeor L1 may be setup. For this purpose, the ,handwheel 8:3 is :shown 'as radially positioning the ball carriage Q overa disc 96 rotatable .from .constant speed motor *9? to drive the cylinder .93 .at a predetermined variable speed and thus rotate the worm shaft '93 on the shaft thereof. Said drive isshown: as also rotating through gears 95] and ice and 'difierential .1113, asecond worm-shafted which'axi'ally positions the carriage 92 of *the second threedimensional cam '90. In this case, 'b is r-i-ntroduced by :positioning the dial 102 from handwheel In! in accordance with b, which rotates the second arm of differential I03 .so that the worm shaft 93' is positioned in accordance with L1b (i e. L2).

Cam 90' is rotated in accordance with the angular position-0f the sight at station as bylany suitable means, such as the handwheel 34 mounted on the shaft of the longpinionr32 which meshes withthe gear 33' on the shaft of'the cam 93'. Handwheel 34, as in the previous form, may be rotated through the proper angleqbz which is indicated on the dial 36. In this case, the two cams are laid out-in the tangent functions of the anglesso that the lift of each pin is proportional to Ho. One pin I I9 is shown as rotating-through pinions I25, a dial having an index pointer 82! and the other pin H9 rotates the-inner dial 43' through pinion I22. The intermediate .indeX pointer 3? normally moves with the dial 43,.as in Fig. '8, but maybe adjusted with respectthereto by a knob 52 which actuates a mechanism similar'to thatoperated by knob 420i Figs. 8 and 9 in'accordance with the-distance representing AH, i. e., the difference in elevation between the two sighting stations (see Fig. 4). Therefore, when index pointers l2! and .31 are matched, Ho will be indicated on the outer stationary dial .25 by the aligned indexes.

As in the previous form of the invention, the solution proposed becomes difficult of mechanical solutionfor angles approaching 90,in which the tangent functions become too large-for mechanical reproduction. To take care of such angles, I propose an additional mechanism as shown at the bottom of Fig. 1 1. In this figure a singie three-dimensional cam [3E3 is provided which is shown as rotated in accordance with 2 from the handwheel 3.4 through bevel-gears l3! and I32, long pinion I33 and gear 1.34. The cam is shown as positioned longitudinally .from or through bevelgears l3l and I32 and threaded shaft .163. The camis laid-out so that the lift of the pin 1 35 thereon represents cot 1cot 2, said pin axially positioning a second three-dimensional cam I36. The lattercamis shown as rotated from the b .handwheel l6! through a pinion I31 and gear 138. The .cam [36 may be so laid out, therefore, that the lift of the pin I39 thereon is proportional to which, it will be seen, =is a solution for H0 in Equation v1 and may be indicated on dial 150. Thus, over a considerable range two indications of the same quantity arrived at by different computing means are exhibited, of which the better, .for a..given condition,may be selected.

Inrallformsofthe invention a continuous flow of data occurs and a continuous simultaneous solution, so that there is substantially no lag and any change in-one variable produces substantially instantaneous change in the value of He indicated -on the machine.

As many-changes could bemade in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description orshown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim and desire to secure by Letters Patent is:

- 1. In a two station system for determining the altitude of an aerial object having a device at each station for determining elevation angles of said object, a calculating mechanism comprising a pair of relatively movable indicators adapted to be matched, means for relatively setting said indicators according to the distance between the stations, a device for positioning one of said indicators in accordance with a cotangent function of one of said angles and altitude, a device for positioning the other of said indicators in accordance with a cotangent function of the other of said angles and altitude, and means for actuating both of said devices in accordance with altitude to match said indicators.

2. In a two station system for determining the altitude of an aerial object having a device at each station for determining elevation angles of said object, a calculating mechanism for equating functions of said elevation angles comprising a pair of relatively movable indicators adapted to be matched, means for adjusting the relative positions of said indicators in accordance with the horizontal distance between said stations, a device for positioning one of said indicators in accordance with the cotangent function of one of said angles and altitude, a device for positioning the other of said indicators in accordance with a cotangent function of the other of said angles and altitude, and means for actuating both of said devices in accordance with altitude to match said indicators.

3. In a two station system for determining the altitude of an aerial object having a device at each station for determining elevation angles of said object, a calculating mechanism for equating functions of said elevation angles comprising a pair of relativel movable indicators adapted to be matched, a device for positioning one of said indicators in accordance with a cotangent function of one of said angles and altitude, a device for positioning the other of said indicators in accordance with the cotangent function of the other of said angles and altitude, means for actuating both of said devices in accordance with altitude to match said indicators, and means for adjusting one of said devices in accordance with the vertical distance between said stations.

4. A computing device for determining the altitude of an aerial target for use in connection with a two station observation system wherein each station is provided with a sighting device movable to measure the elevational angle of a target together with means for actuating the computing device in proportion to the degree of movement of the respective sighting devices, the improvement which comprises a pair of cams in said computing device, each adapted to be turned on its axis in accordance with the angle of elevation of the target from the respective stations, a lift pin for each cam, said cams being laid out circumferentially so as to move the associated lift pin in accordance with a cotangent function of the angle at which the associated sighting device is moved and longitudinally in accordance with the height of the target, an indicating scale having a rotary index controlled by the movement of one of said lift pins, a cooperating pointer coaxially disposed in respect to said index adapted to be turned by the movement of the other lift pin, and common movable means for translating the cams, the movement of the common means required to match the pointer with the scale being proportional to the height of the target.

5. In a computing device for determining the altitude of an aerial target for use in connection with a two station observation system wherein each station -is provided with a sighting device movable to measure the elevational angle of a target, the improvement which comprises a pair of three dimensional cams in said computing device adapted to be turned in accordance with the elevation angle of the target from the respective stations, a lift pin for each cam, said cams being laid out circumferentially so as to move the associated lift pin in accordance with a cotangent function of the angle at which the associated sighting device is moved, said cams being also laid out longitudinally in a function of the altitude of the target, an indicating scale having a rotary index controlled by the movement of one of said lift ins and cooperating pointer means coaxially disposed in respect to said index adapted to be turned by the other lift pin, means for moving said cams in an axial direction to match said index and pointer, and an indicating device operated by the last mentioned means from which the altitude may be read when the index and pointer are matched.

6. A computing device according to claim 5 in which said cams are mounted in carriage, and in which means are provided for moving said carriage to impart uniform axial movement to said cams.

7. A computing device according to claim 5 in which said cams are mounted in a carriage, and in which the means for moving the cams comprise a threaded shaft having a crank thereon connected to the carriage, and in which the indicating device from which altitude may be read comprises a revolution counter driven from the last mentioned shaft.

8. A computing device according to claim 5 in which said pointer means comprise a pair of coaxially disposed pointers having adjusting means by which the angular distance between the pointers may be adjusted in proportion to the distance between the two observation stations.

9. A computing device according to claim 5 in which the computing mechanism is disposed at one of said stations, the sighting device thereat being connected to one of the cams by a gear train.

10. A computing device according to claim 5 in which the computing mechanism is disposed at one of the stations and the angular movement of the sighting device at the other station is transmitted to the computing device over electric circuit means.

11. A computing device according to claim 5 in which said cams are mounted in a carriage, and in which means are provided for moving said carriage to impart a uniform axial movement to said cams, and in which means are provided to produce relative axial movement of the cams in the carriage to compensate for height difference between the stations.

12. A computing device for determining the altitude of an aerial target for use in connection with two spaced sighting stations and operating on the altimetric roof principle, said computing device comprising a pair of three dimension cams associated with the respective stations, a support in which said cams are movable in rotary as well as axial directions, a lift pin for each cam responsive to the movement thereof, means in said computing device to move said cams inde- 9, pendently in one of said directions in proportion to the elevational angles of. a. target as determined by. therespective sighting stations, the cams being laid out in. the latter dimension in accordance :with a cotangent function andin accordance with altitude in the other dimension, common means for moving said cams in the other of said directions, cooperating indicator members actuated by the resulting movement of, said lift pins, and means'f'or offsetting one indicator member proportionally to the distance between the sighting stations, whereby the height of the target is indicated when said common means is moved to cause theindicator members. tomatch.

13. A computing device for determining the altitude of an aerial target for use in connection with a pair of spaced sighting stations and operating on the altimetric roof principle, said computing device comprising a pair of cams associated with the respective stations, a lift pin for each cam, a support in which said cams are movable in rotary as well as axial directions, said cams bein laid out in one dimension in accordance with a cotangent function of the angular position of the sighting device associated therewith, and in another dimension in a function of the altitude of the target, means in said computing device for moving said cams respectively in one of said directions so that the lift pins are displaced in accordance with a cotangent function of the elevational angle of the target as determined by the respective sighting stations, common means for moving the cams in the other of said directions, cooperating indicator members actuated by the resulting movement of said lift pins, and means for offsetting one indicator member proportionally to the distance between the sighting stations, whereby the height of the target is indicated when the common means is moved to cause the indicator members to match.

14. In a computer for determining the altitude of an aerial object, a pair of three dimension cams, separate means for displacing the cams in one dimension accordin to elevation angle data of the object obtained from individual spaced sighting stations, a lift pin for each cam, a pair of cooperating index members, each member being displaced by one of the lift pins, means for relatively positioning the cams in another dimension in accordance with the space between the sighting stations, common means for further displacing the cams in the last-mentioned dimension to cause the index members to match, the cams being so laid out that the displacement thereof by the common means required to match the index members is proportional to the altitude of the object.

15. In a computer for determining the altitude of an aerial target, a pair of three dimension cams, separate means for displacing the cams in one dimension in accordance with the angles of elevation of the target obtained from separate observation positions, common displaceable means for adjusting the cams in another dimension, means for further adjusting one of the cams in the last-mentioned dimension in accordance with the distance between the observation positions, indicating means controlled by the cams adapted to be matched through the displacement thereof by the common means, the cams being so laid out that the displacement of the common means required to match the indicating means is in proportion to the altitude of the target.

16. In a computer for determining the altitude of an aerial object, a pair of three dimension cams, separatemeans for displacing the respectivecams in-one dimension according to elevation angle dataof the object obtained from two spaced sighting stations, a heightindicating device, common means for adjusting the cams in another dimension together with the height indicating device,a liftpin. for each. cam, a pair of cooperating index members each displaced by one of thelift pins, setting means for offsetting one index. member withr espect to the associated lift pin-in accordance with the distance between the sightingistations, the cams-being so laid-out that when adjusted by the common means to cause the indexes to match, the indicating device will indicate the height of the object due to the resulting adjustment thereof.

17. In a computer for determining the altitude of an aerial object, a pair of three dimension cams, a common movable frame within which the cams are supported for rotation, means for respectively displacing each cam in rotation according to elevation angle data of the object determined by individual spaced sighting stations, means for moving the frame to translate the cams, a lift pin for each cam, cooperating indicators respectively actuated by the lift pins, means for offsetting one indicator with respect to the associated lift pin in proportion to the distance between the stations, the cams being so laid out that the displacement of the frame necessary to match the indicators is proportional to the altitude of the object.

18. In a computer for determining the altitude of an aerial object, a pair of three dimension cams, a common movable frame within which the cams are supported for rotation, means for displacing each cam in rotation respectively according to elevation angle data of the object determined by individual spaced sighting stations, a height indicating device, common means effective to'move the frame to translate the cams and to simultaneously operate the height indicating device to effect a corresponding change in the height value indicated thereby, a lift pin for each cam, a pair of cooperating index members each displaced by one of the lift pins, one of the index members being offset from the associated lift pin in accordance with the space between the sighting stations, the cams being so laid out that when the frame is adjusted by the common means to cause the indexes to match, the resulting operation of the height indicating device will provide an indication of the height of the object.

19. A computer for determining the altitude of an aerial object according to claim 18, having further means for axially adjusting one of the cams within the frame to compensate for difference in elevation of the sighting stations.

20. In a computer for determining the altitude of an aerial object, a pair of three dimensional cams, separate means for displacing the cams re spectively in one dimension according to elevation angle data of the object obtained from two spaced sighting stations, a height indicating device, common means for displacing both cams in another dimension together with the height indicating device, a lift pin for each cam, a pair of cooperating index members each displaced by one of the lift pins, setting means for offsetting one index with respect to the associated lift pin in accordance with the distance between the sighting stations, the cams loeing so laid out that when so displaced by the common means as to 11 12 match the indexes, the height indicating means Number Name Date indicates the altitude of the object. 135 49 Nieman Man 25, 1930 EARL CHAFEE- 722,435 Sorensen Mar. 1903 2,294,417 Morrison Sept. 1, 1942 REFERENCES CITED 5 1,345,697 Routin July 6, 1920 The following references are of record in the file of this patent: FQR'EIGN PATENTS UNITED STATES PATENTS Number Country Date Number Name Date 10 332,132 Germany Jan. 25, 1921 1,408,504 Hammond et a1 Mar. 7, 1922 1,345,706 Routin July 6, 1920 OTHER REFERENCES 1,345,701 Routin July 6, 19 0 Coast Artillery Field Manual (1933), Supt. of 1,453,104.- Gray Apr. 24, 1923 Documents, Washington, D. C. 

